Question

My DataGridView control currently sorts using the Sort property of the bound data, but it isn’t doing what I want it to do.

I have a column called Employee that is displayed as “Firstname Lastname”.

When I sort by Employee, Amy Z_Lastname is listed before John A_Lastname, meaning I would prefer to sort by last names.

I could break the Employee string up into 3 parts, include those in the DataTable, and set the sort to “Lastname, Firstname”, then hide the Lastname and Firstname columns.

I’d rather learn how to override the default IComparer (or whatever it uses) to provide instructions on how to sort the way I want (the answer I’d prefer).

Answer 1

Custom sorting in the DataGridView

The DataGridView knows nothing of this
ranking, of course. The default
sorting scenario (automatic sorting
for a data-bound column) of invoking
DataGridView.Sort() via a column
header mouse click simply delegates to
the IBindingList implementation of
ApplySort() in the list you’ve bound
to the grid. Normally, this list
would be a DataView. Using my
ObjectListView implementation, this
would be a view of a list of arbitrary
business objects. Either way, you end
up comparing the properties of the
items in the list using the
IComparable implementation of the
property type.

Details

The PropertyComparers property exposes
a PropertyComparersCollection, which
is a dictionary of property name keys
and IComparer values. You can replace
the IComparer for a property by using
the PropertyComparersCollection.Add()
method or the indexer (e.g.
view.PropertyComparers[“PropName”] =
myComparer). To revert to the default
IComparable sorting, use the
PropertyComparersCollection.Remove()
method or set the IComparer value to
null via the indexer.

If an IComparer is added to the
PropertyComparers collection, it will
be used for all subsequent sorts until
it is removed from the collection or
it is replaced with another IComparer.
If the ObjectListView is already
sorted when an IComparer is added to
or removed from PropertyComparers, the
view will automatically be re-sorted.

If you want to change multiple
property comparers after the view is
sorted, you can use the ObjectListView
BeginUpdate() and EndUpdate() methods
to suppress the ListChanged and Sort
events until all of the IComparers
have been changed. This prevents
multiple refreshes of the
DataGridView. If the ObjectListView
is not sorted at the time IComparers
are added or removed, no automatic
re-sorting is done.

Note that when sorting on multiple
columns, a custom IComparer can be
used with one sort property, and the
default IComparable sort on another.

e.g:

private void radioButtonSortProgram_CheckedChanged(object sender, EventArgs e)

{

    if (this.radioButtonSortProgramAlpha.Checked)

        this.view.PropertyComparers["Program"] = new CustomerProgramComparerAlpha();

    else if (this.radioButtonSortProgramRank.Checked)

        this.view.PropertyComparers["Program"] = new CustomerProgramComparerRank();

    else

        this.view.PropertyComparers.Remove("Program");

}